1. Field of the Invention
The present invention relates generally to the field of electrical connectors. More specifically, the present invention discloses a non-invasive connector used in testing of integrated circuit packages.
2. Statement of the Problem
Many modern integrated circuits, and in particular microprocessor chips, have a large number of external leads which greatly complicates effective testing. In the past, an integrated circuit was usually connected to a printed circuit board by insertion into a socket having pins that extended through the board. The pins are soldered to the appropriate signal traces on the board to establish the desired connections for the integrated circuit leads. These pins also provide a ready means to establish temporary connections for testing of the integrated circuit after its installation.
More recently, surface mount technology has gained wide acceptance. Using this technology, the integrated circuit leads are directly soldered to signal traces on the surface of the printed circuit board. Surface mount technology offers many advantages including reduced manufacturing costs and space savings. However, it significantly increases the difficulty of testing an integrated circuit after installation due to the absence of socket pins to provide connections. Instead, it becomes necessary to make direct contact with each of the integrated circuit leads. The close spacing typically found between adjacent integrated circuit leads makes proper alignment of the testing leads difficult. For example, a common package used for microprocessors is a quad flat pack with 132 leads located on 0.025 inch centers. Improper alignment of the testing leads can cause a testing lead to: (1) fail to make contact with the appropriate integrated circuit lead; (2) con the wrong integrated circuit lead; or (3) short two adjacent integrated circuit leads. Any of these conditions will result in incorrect testing results and can also damage the integrated circuit being tested. In addition, improper alignment can result in mechanical damage to an integrated circuit lead or to the solder joint between the lead and the signal trace on the board, due to the fact that surface mounted devices tend to have leads that are very soft and delicate. Furthermore, improper alignment can result in mechanical and electrical damage to the testing leads and related equipment.
A number of devices have been invented in the past to provide connections with the leads of integrated circuit packages, including the following:
______________________________________ Inventor Patent No. Issue Date ______________________________________ Kabadi 4,917,613 Apr. 17, 1990 Yen 4,084,869 Apr. 18, 1978 Cedrone 4,866,374 Sep. 12, 1989 Cedrone 4,747,784 May 31, 1988 Payne 4,716,500 Dec. 29, 1987 ______________________________________
Kabadi discloses a connector for coupling electrical cables with an integrated circuit socket 701. A stiffener plate 521 shown in FIGS. 5 and 7 has outwardly extending combs along each of its four outside edges 511, 512, 513, and 514. These combs are used to provide positive contact between the contact pads of the flexible circuits and the contacts 715, 716, 717, and 718 of the socket 701. It should be noted that the teeth of these combs are shown in alignment with the socket contacts in FIG. 7. This is directly contrary to the present invention in which the comb teeth are inserted between the leads of the integrated circuit to provide connector alignment and to maintain electrical separation between the leads.
Yen discloses an interconnector for integrated circuit packages 20. The interconnector components 22, 24 are inserted between the integrated circuit 20 and its normal socket 12 to allow monitoring of electrical signals to and from the integrated circuit.
Cedrone discloses two variations on a contactor assembly for testing surface-mounted integrated circuits prior to their installation. In both patents, an array of conductive test leads 32 are used to contact the leads of the device 22 under test.
Payne discloses a probe cable assembly for testing microprocessor systems where the microprocessor is packaged on a leadless chip carrier (i.e. a ceramic substrate with a pattern of planar contact pads flush with its underside). During testing, the microprocessor is first removed from its socket and replaced with a probe element 43 having a corresponding pattern of contact pads 42.
3. Solution to the Problem
None of the prior art references uncovered in the search disclose a connector having the comb structure of the present invention which insures proper alignment of the connector with respect to the integrated circuit leads and also provides mechanical separation and electrical insulation between the integrated circuit leads.